Fibromuscular dysplasia of the brachial artery in patients with spontaneous coronary artery dissection: a case series and literature review.

Spontaneous coronary artery dissection (SCAD) is diagnosed in a very small percentage of patients with suspected acute coronary syndromes who undergo emergency coronary angiography. Although fibromuscular dysplasia (FMD) is known to coexist in patients with SCAD, the vascular sites of FMD and their frequency have not yet been clarified. We retrospectively reviewed the medical records of 16 patients who were diagnosed with and treated for SCAD at our hospital between 1 January 2011 and 31 January 2023. We have summarized their baseline and clinical characteristics and medical variables, including coronary and upper extremity angiography and in-hospital outcomes. One of our patients had concurrent cardiac tamponade requiring pericardial drainage, and another went into hemorrhage shock the following day from dissection of the gastric retroperitoneal artery. Characteristic angiographic features of partial or diffuse nonatherosclerotic stenosis were observed mainly in the distal parts of the coronary arteries or their branches. Notably, in six patients with SCAD who underwent upper extremity angiography, FMD of the brachial artery was revealed. For the first time, to our knowledge, we found a high prevalence of multifocal FMD of the brachial artery in patients with SCAD.

Characteristics, Antithrombotic Patterns, and Prognostic Outcomes in Claudication and Critical Limb-Threatening Ischemia Undergoing Endovascular Therapy.

PURPOSE: The underlying difference between intermittent claudication (IC) and critical limb-threatening ischemia (CLTI) still remains unclear. This prospective multicenter observational study aimed to clarify differences in clinical features and prognostic outcomes between IC and CLTI, and prognostic factors in patients undergoing endovascular therapy (EVT). MATERIALS AND METHODS: A total of 692 patients with 808 limbs were enrolled from 20 institutions in Japan. The primary measurements were the 3-year rates of major adverse cardiovascular event (MACE) and reintervention. RESULTS: Among patients, 79.0% had IC and 21.0% had CLTI. Patients with CLTI were more frequently women and more likely to have impaired functional status, undernutrition, comorbidities, hypercoagulation, hyperinflammation, distal artery disease, short single antiplatelet and long anticoagulation therapies, and late cilostazol than patients with IC. Aortoiliac and femoropopliteal diseases were dominant in patients with IC and infrapopliteal disease was dominant in patients with CLTI. Patients with CLTI underwent less frequently aortoiliac intervention and more frequently infrapopliteal intervention than patients with IC. Longitudinal change of ankle-brachial index (ABI) exhibited different patterns between IC and CLTI (pinteraction=0.002), but ABI improved after EVT both in IC and in CLTI (p<0.001), which was sustained over time. Dorsal and plantar skin perfusion pressure in CLTI showed a similar improvement pattern (pinteraction=0.181). Distribution of Rutherford category improved both in IC and in CLTI (each p<0.001). Three-year MACE rates were 20.4% and 42.3% and 3-year reintervention rates were 22.1% and 46.8% for patients with IC and CLTI, respectively (log-rank p<0.001). Elevated D-dimer (p=0.001), age (p=0.043), impaired functional status (p=0.018), and end-stage renal disease (p=0.019) were independently associated with MACE. After considering competing risks of death and major amputation for reintervention, elevated erythrocyte sedimentation rate (p=0.003) and infrainguinal intervention (p=0.002) were independently associated with reintervention. Patients with CLTI merely showed borderline significance for MACE (adjusted hazard ratio 1.700, 95% confidence interval 0.950-3.042, p=0.074) and reintervention (adjusted hazard ratio 1.976, 95% confidence interval 0.999-3.909, p=0.05). CONCLUSIONS: The CLTI is characterized not only by more systemic comorbidities and distal disease but also by more inflammatory coagulation disorder compared with IC. Also, CLTI has approximately twice MACE and reintervention rates than IC, and the underlying inflammatory coagulation disorder per se is associated with these outcomes. CLINICAL IMPACT: The underlying difference between intermittent claudication (IC) and critical limb-threatening ischemia (CLTI) still remains unclear. This prospective multicenter observational study, JPASSION study found that CLTI was characterized not only by more systemic comorbidities and distal disease but also by more inflammatory coagulation disorder compared to IC. Also, CLTI had approximately twice major adverse cardiovascular event (MACE) and reintervention rates than IC. Intriguingly, the underlying inflammatory coagulation disorder per se was independently associated with MACE and reintervention. Further studies to clarify the role of anticoagulation and anti-inflammatory therapies will contribute to the development of post-interventional therapeutics in the context of peripheral artery disease.

Comparison of left ventricular pacing performance among pre-shaped guidewires designed for transfemoral-approach transcatheter aortic valve implantation.

TAVI is an established therapy for patients with severe aortic stenosis. Rapid or control pacing is necessary for TAVI, and most centers are familiar with right ventricular (RV) pacing. Although there are several reports on the efficacy and safety of LV pacing, they are still few. In addition, LV pacing has not been studied for different LV guidewires. Our aim is to study the effectiveness of left ventricular (LV) pacing and the thresholds of LV guidewires in patients who underwent transcatheter aortic valve implantation (TAVI). We retrospectively analyzed 252 consecutive patients who underwent trans-femoral TAVI (TF-TAVI) with LV pacing in our institute between December 2017 and November 2020. We excluded 48 patients from the total cohort due to TAVI with RV pacing, and the remaining 204 patients were analyzed (52 males, mean age 85 ± 5 years). Among them, 202 patients (99.0%) had successful LV pacing. In the two patients with failed LV pacing, SAFARI2™ Small was used. The CONFIDA™ group (n = 34) showed a significantly lower threshold than the SAFARI2™ group (n = 163) (median 3.0 vs. 5.0 V; P = 1.1 × 10-7). LV pacing with Lunderquist® was successful in all patients (n = 7). LV pacing in TAVI was an effective and safe strategy. CONFIDA™ wire may be particularly well suited for LV pacing in TAVI.

Impella Motor Current Amplitude Reflects the Degree of Left Ventricular Unloading under ECPELLA Support.

The combination of venoarterial extracorporeal membrane oxygenation (VA-ECMO) and Impella, referred to as ECPELLA, is a powerful transient mechanical circulatory support for patients with severe cardiogenic shock (CS). During ECPELLA support, VA-ECMO loads the left ventricle (LV) and Impella unloads the LV. Therefore, evaluating the degree of LV unloading during ECPELLA may be a prerequisite to protect the injured myocardium. Here we report a patient with CS due to an inferior ST-elevation myocardial infarction in which the degree of LV unloading on ECPELLA was confirmed by direct LV pressure (LVP) measurement. After the percutaneous coronary intervention for the right coronary artery on ECPELLA, the aortic pressure became nonpulsatile and the peak systolic LVP was reduced at approximately 10 mmHg with 20 mA of the Impella motor current (MC) amplitude, which we referred to as the total LV unloading condition. We maintained the condition in the early phase of ECPELLA by monitoring the Impella MC amplitude at 20 mA and less with nonpulsatile aortic pressure. The patient was successfully weaned off VA-ECMO on day 3, and Impella was explanted on day 8. Prior to the Impella explant, the Impella MC amplitude increased more than 100 mA and the estimated pressure gradient between the aortic pressure and LVP was well matched with the directly measured LVP. In this case, the patient was successfully treated by ECPELLA with the total LV unloading condition, and we showed that the degree of LV unloading on ECPELLA can be estimated from the aortic pressure and Impella MC amplitude at given Impella flows.

Questionnaire in patients with aborted sudden cardiac death due to coronary spasm in Japan.

OBJECTIVES: We investigated the medical or mechanical therapy, and the present knowledge of Japanese cardiologists about aborted sudden cardiac death (ASCD) due to coronary spasm. METHODS: A questionnaire was developed regarding the number of cases of ASCD, implantable cardioverter-defibrillator (ICD), and medical therapy in ASCD patients due to coronary spasm. The questionnaire was sent to the Japanese general institutions at random in 204 cardiology hospitals. RESULTS: The completed surveys were returned from 34 hospitals, giving a response rate of 16.7%. All SCD during the 5 years was observed in 5726 patients. SCD possibly due to coronary spasm was found in 808 patients (14.0%) and ASCD due to coronary spasm was observed in 169 patients (20.9%). In 169 patients with ASCD due to coronary spasm, one or two coronary vasodilators was administered in two-thirds of patients [113 patients (66.9%)], while more than 3 coronary vasodilators were found in 56 patients (33.1%). ICD was implanted in 117 patients with ASCD due to coronary spasm among these periods including 35 cases with subcutaneous ICD. Majority of cause of ASCD was ventricular fibrillation, whereas pulseless electrical activity was observed in 18 patients and complete atrioventricular block was recognized in 7 patients. Mean coronary vasodilator number in ASCD patients with ICD was significantly lower than that in those without ICD (2.1 ± 0.9 vs. 2.6 ± 1.0, p < 0.001). Although 16 institutions thought that the spasm provocation tests under the medications had some clinical usefulness of suppressing the next fatal arrhythmias, spasm provocation tests under the medication were performed in just 4 institutions. CONCLUSIONS: In the real world, there was no fundamental strategy for patients with ASCD due to coronary spasm. Each institution has each strategy for these patients. Cardiologists should have the same strategy and the same knowledge about ASCD patients due to coronary spasm in the future.

A unique intracellular compartment formed during the oligotrophic growth of Rhodococcus erythropolis N9T-4.

Rhodococcus erythropolis N9T-4, isolated from stored crude oil, shows extremely oligotrophic features and can grow on a basal medium without any additional carbon, nitrogen, sulfur, and energy sources, but requires CO2 for its oligotrophic growth. Transmission electron microscopic observation showed that a relatively large and spherical compartment was observed in a N9T-4 cell grown under oligotrophic conditions. In most cases, only one compartment was observed per cell, but in some cases, it was localized at each pole of the cell, suggesting that it divides at cell division. We termed this unique bacterial compartment an oligobody. The oligobody was not observed or very rarely observed in small sizes under nutrient rich conditions, whereas additional carbon sources did not affect oligobody formation. Energy dispersive X-ray spectroscopy analysis revealed remarkable peaks corresponding to phosphorus and potassium in the oligobody. The oligobodies in N9T-4 cells could be stained by Toluidine blue, suggesting that the oligobody is composed of inorganic polyphosphate and is a type of acidocalcisome. Two genes-encoding polyphosphate kinases, ppk1 and ppk2, were found in the N9T-4 genome: ppk1 disruption caused a negative effect on the formation of the oligobody. Although it was suggested that the oligobody plays an important role for the oligotrophic growth, both ppk-deleted mutants showed the same level of oligotrophic growth as the wild-type strain.

Impact of Killip classification on acute myocardial infarction: data from the SAIKUMA registry.

Therapeutic devices for acute myocardial infarction (AMI) have evolved dramatically in recent years. However, the impact of the Killip classification of AMI outcomes in patients undergoing aggressive percutaneous coronary intervention remains unclear. We performed a 10-year retrospective review of 2062 patients diagnosed with AMI, and divided the data into two 5-year intervals: 2005-2009 (n = 1071), and 2010-2014 (n = 991). No difference was observed in in-hospital mortality rate between the two periods (first period, 11.5% vs second period, 9.7%; P = 0.19). The incidence of stent thrombosis was not significantly different between the two periods, and very few thrombi occurred in patients who received second-generation drug-eluting stents (DES) (0.98%: 5/511). In-hospital mortality due to stent thrombosis was high in the full cohort (15%). During the second period, in-hospital mortality was lower in Killip class 4 patients, although the difference was not significant (59.1 vs 47.5%, P = 0.07). Multivariable logistic regression identified several factors that significantly affected in-hospital mortality, including age [odds ratio (OR) 1.07], left main trunk (OR 2.47), peak CPK value above 5000 IU/L (OR 3.18), and Killip class 4 (OR 15.63). We evaluated trends in in-hospital mortality among patients with AMI over a 10-year period. New DES and the frequent use of mechanical support in patients with hemodynamic compromise tended to improve in-hospital mortality, but the effect was not significant. Notably, Killip class 4 on admission was associated with an estimated 16-fold increased risk of in-hospital death.

A lotus root-like appearance in both the left anterior descending and right coronary arteries.

A 60-year-old man was referred to our hospital because of dyspnea on exertion. He was diagnosed with heart failure due to an old myocardial infarction. Myocardial stress perfusion scintigraphy revealed inducible myocardial ischemia. Coronary angiography revealed hazy slit lesions in both the left anterior descending (LAD) and right coronary arteries (RCA). We first performed percutaneous coronary intervention (PCI) on the LAD lesion. Subsequently, we performed PCI for the RCA lesion using multiple imaging modalities. We observed a lotus root-like appearance in both the LAD and RCA, and PCI was successful for both vessels. We describe this rare case in detail.

Resting angina due to papillary fibroelastoma of the right coronary cusp.

A 63-year-old man with chest pain at rest was referred to our hospital. Transthoracic echocardiography showed a mobile ball-like mass at the top of the right coronary cusp. Subsequently, transesophageal echocardiography also showed a mobile mass at the right coronary cusp. Aortic valve replacement with a mechanical valve was performed under general anesthesia. We diagnosed this condition as papillary fibroelastoma based upon the pathological findings with hematoxylin and eosin staining, and Elastica van Gieson staining. Coronary angiography revealed no organic lesions. The operation was successful, and the patient remains asymptomatic. We speculate that the resting chest pain was induced by transient occlusion of the right coronary orifice by the tumor. We describe this rare case in detail including a review of the literature.

Impact of shear stress and atherosclerosis on entrance-tear formation in patients with acute aortic syndromes.

Weak aortic media layers can lead to intimal tear (IT) in patients with overt aortic dissection (AD), and aortic plaque rupture is thought to progress to penetrating atherosclerotic ulcer (PAU) with intramural hematoma (IMH). However, the influences of shear stress and atherosclerosis on IT and PAU have not been fully examined. Ninety-eight patients with overt AD and 30 patients with IMH and PAU admitted to our hospital from 2002 to 2007 were enrolled. The greater curvatures of the aorta, including the anterior and right portions of the ascending aorta and anterior portion of the aortic arch, were defined as sites of high shear stress. The other portions of the aorta were defined as sites of low shear stress based on anatomic and hydrodynamic theories. Aortic calcified points (ACPs) were manually counted on computed tomography slices of the whole aorta every 10 mm from the top of the arch to the abdominal bifurcation point. IT was more often observed at sites of high shear stress in overt AD than in PAU (73.5 vs 20.0 %, P < 0.0001). Significantly more ACPs were present in PAU than in overt AD (18.6 ± 8 vs 13.3 ± 10, P = 0.007). The present study suggests that high shear stress and less severe atherosclerosis could induce the occurrence of an IT, thereafter progressing to overt AD, and that low shear stress and more severe atherosclerosis could proceed to PAU with IMH. These findings may help to identify the entrance-tear site.

Efficacy and safety of post-closure technique using Perclose ProGlide/ProStyle device for large-bore mechanical circulatory support access sites.

PURPOSE: Mechanical circulatory support (MCS) using a venoarterial extracorporeal membrane oxygenation (VA-ECMO) device or a catheter-type heart pump (Impella) is critical for the rescue of patients with severe cardiogenic shock. However, these MCS devices require large-bore cannula access (14-Fr and larger) at the femoral artery or vein, which often requires surgical decannulation. METHODS: In this retrospective study, we evaluated post-closure method using a percutaneous suture-mediated vascular closure system, Perclose ProGlide/ProStyle (Abbott Vascular, Lake Bluff, IL, Perclose), as an alternative procedure for MCS decannulation. Closure of 83 Impella access sites and 68 VA-ECMO access sites performed using Perclose or surgical method between January 2018 and March 2023 were evaluated. RESULTS: MCS decannulation using Perclose was successfully completed in all access sites without surgical hemostasis. The procedure time of ProGlide was shorter than surgical decannulation for both Impella and VA-ECMO (13 min vs. 50 min; p < 0.001, 21 min vs. 65 min; p < 0.001, respectively). There were no significant differences in the 30-day survival rate and major adverse events by decannulation including arterial dissection requiring endovascular treatment, hemorrhage requiring a large amount of red blood cell transfusion, and access site infection. CONCLUSION: Our results suggest that the post-closure technique using the percutaneous suture-mediated closure system appears to be a safe and effective method for large-bore MCS decannulation.

Role of Common Antihypertensives in the Growth of Abdominal Aortic Aneurysm at the Presurgical Stage.

Background: Whether drug therapy slows the growth of abdominal aortic aneurysms (AAAs) in the Japanese population remains unknown. Methods and Results: In a multicenter prospective open-label study, patients with AAA at the presurgical stage (mean [±SD] AAA diameter 3.27±0.58 cm) were randomly assigned to treatment with candesartan (CAN; n=67) or amlodipine (AML; n=64) considering confounding factors (statin use, smoking, age, sex, renal function), with effects of blood pressure control minimized setting a target control level. The primary endpoint was percentage change in AAA diameter over 24 months. Secondary endpoints were changes in circulating biomarkers (high-sensitivity C-reactive protein [hs-CRP], malondialdehyde-low-density lipoprotein, tissue-specific inhibitor of metalloproteinase-1, matrix metalloproteinase [MMP] 2, MMP9, transforming growth factor-ß1, plasma renin activity [PRA], angiotensin II, aldosterone). At 24 months, percentage changes in AAA diameter were comparable between the CAN and AML groups (8.4% [95% CI 6.23-10.59%] and 6.5% [95% CI 3.65-9.43%], respectively; P=0.23]. In subanalyses, AML attenuated AAA growth in patients with comorbid chronic kidney disease (CKD; P=0.04) or systolic blood pressure (SBP) <130 mmHg (P=0.003). AML exhibited a definite trend for slowing AAA growth exclusively in never-smokers (P=0.06). Among circulating surrogate candidates for AAA growth, PRA (P=0.02) and hs-CRP (P=0.001) were lower in the AML group. Conclusions: AML may prevent AAA growth in patients with CKD or lower SBP, associated with a decline in PRA and circulating hs-CRP.

Incidence, Risk Factors, and Treatment of Venous Thromboembolism after a Serious Disaster: The Kumamoto Twin Earthquakes.

Objective: On April 16, 2016, earthquakes struck Kumamoto. In this report, the incidence and treatment of venous thromboembolism (VTE) in patients presenting to our hospital are summarized. Materials and Methods: We reviewed the details of 22 consecutive patients who were diagnosed with VTE at our hospital during the 2 weeks after the earthquakes. Results: Nineteen of the 22 patients stayed in their cars overnight after the earthquakes. Particularly, during the first 4 days, seven consecutive patients were hospitalized for pulmonary thromboembolism. All seven patients had sheltered in their cars after the earthquakes. The two patients transported on days 2.42 and 3.54 were the most severe cases. One patient was admitted after emergency initiation of venoarterial extracorporeal membrane oxygenation for treatment of hemodynamic collapse, whereas the other patient was admitted after resuscitation. By contrast, deep vein thrombosis (DVT) alone occurred within 5-9 days of the earthquakes. Bilateral DVT was the most common, which was followed by DVT on the right side only. Conclusion: The incidence of VTE might be higher after an earthquake, and an overnight stay in a car might be a risk factor for VTE. Stable patients based on the D-dimer concentration can be managed with nonwarfarin oral anticoagulants.

Clinical impacts of CT-derived fractional flow reserve under insurance reimbursement: Results from multicenter, prospective registry.

BACKGROUND: Although computed tomography-derived fractional flow reserve (FFRCT) has been reimbursed in a few countries, its impacts on daily practice of coronary artery diseases are not fully elucidated. We evaluated the clinical impacts of FFRCT under the real Japanese insurance reimbursement. METHODS: In the multicenter prospective registry: DYNAMIC-FFRCT study, a total of 410 patients who underwent FFRCT analysis under reimbursement were prospectively enrolled at 6 Japanese sites from October 2019 to November 2021. Coronary CT angiography and FFRCT findings, treatment plans, and 90-day outcomes were recorded. The primary endpoint was the redirection rate from the tests that might be expected without FFRCT [invasive coronary angiography (ICA)-selected group, myocardial perfusion single photon emission CT (MPS)-selected group, optimal medical therapy (OMT)-selected group, and others-selected group] to those that were actually performed based on FFRCT. RESULTS: ICA could be avoided in 39.5 % in the ICA-selected group (N = 233). In particular, in 94.3 % of patients with an FFRCT value of >0.80, additional examinations, such as ICA, were avoided. In addition, in the MPS-selected group (N = 133), 92.6 % had no additional tests with FFRCT > 0.80, while only 2 cases with FFRCT ≤ 0.80 underwent additional MPS examination. On the contrary, 33.3 % of the OMT-selected group (N = 33) had FFRCT ≤ 0.80. Approximately, 35 % medical cost reduction was also finally expected. CONCLUSION: Introduction of FFRCT could not only reduce unnecessary ICA and be a test that replaces the conventional non-invasive functional assessment modality but also result in medical cost reduction even when used under real Japanese insurance reimbursement.

Inappropriate sinus tachycardia-induced cardiomyopathy with severe functional mitral regurgitation and successful treatment with ivabradine.

Ivabradine increases stroke volume, but does not have a negative impact on blood pressure (BP). Thus, a patient with low BP can benefit from treatment with ivabradine. A 72-year-old Japanese woman with asthma and chronic bronchitis presented with dyspnea. Her heart rate (HR) was 126 beats per minute and an electrocardiogram showed sinus tachycardia. The chest X-ray showed cardiomegaly and pulmonary congestion. A transthoracic echocardiogram (TTE) showed reduced left ventricular ejection function (LVEF) and severe functional mitral regurgitation (MR). We diagnosed her with inappropriate sinus tachycardia (IST) and heart failure (HF) due to tachycardia-induced cardiomyopathy. After resolving the pulmonary congestion with diuretics, we administered a minimum dose of bisoprolol, which resulted in re-exacerbation of the HF. Because IST was persistent, we initiated treatment with ivabradine. As soon as ivabradine was started, the HR decreased, the BP gradually increased, and HF compensation was achieved. Bisoprolol was continued and losartan was started. In summary, we used ivabradine for a patient with tachycardia, low BP, a low LVEF, and severe MR. By optimizing the medical therapy, exercise tolerance improved and she was discharged. The serum brain natriuretic peptide was significantly reduced and TTE showed an improved LVEF and reduced MR. .

Transfemoral Transcatheter Aortic Valve Implantation by Three-Dimensional Computed Tomography/Fluoroscopy Fusion Imaging Guidance in a Patient With Right-Sided Aortic Arch and Chronic Aortic Dissection.

Transcatheter aortic valve implantation (TAVI) represents the standard of care for relieving aortic stenosis in high-risk patients for surgery. The transfemoral approach is preferable with respect to invasiveness, but is often difficult in patients with complex vascular structures. Recently, the clinical application of advanced visualization and guidance technology with three-dimensional computed tomography (3D-CT) during TAVI has received considerable attention. Herein we report successful transfemoral TAVI in a patient with a right-sided aortic arch and chronic aortic dissection without vascular complications by 3D-CT/fluoroscopy fusion imaging guidance.

Impact of extracorporeal CPR with transcatheter heart pump support (ECPELLA) on improvement of short-term survival and neurological outcome in patients with refractory cardiac arrest - A single-site retrospective cohort study.

Aim: Extracorporeal cardiopulmonary resuscitation (E-CPR) using veno-arterial extracorporeal membrane oxygenation (VA-ECMO) is a novel lifesaving method for refractory cardiac arrest. Although VA-ECMO preserves end-organ perfusion, it may affect left ventricular (LV) recovery due to increased LV load. An emerging treatment modality, ECPELLA, which combines VA-ECMO and a transcatheter heart pump, Impella, can simultaneously provide circulatory support and LV unloading. In this single-site cohort study, we assessed impact of ECPELLA support on clinical outcomes of refractory cardiac arrest patients. Method: We retrospectively reviewed 165 consecutive cardiac arrest patients, who underwent E-CPR by VA-ECMO with or without intra-aortic balloon pump (IABP) or ECPELLA from January 2012 to September 2021. We assessed 30-day survival rate, neurological outcome, hemodynamic data, and safety profiles including hemolysis, acute kidney injury, blood transfusion and embolic cerebral infarction. Results: Among 165 E-CPR patients, 35 patients were supported by ECPELLA, and 130 patients were supported by conventional VA-ECMO with or without IABP. Following propensity score matching of 30 ECPELLA and 30 VA-ECMO patients, the 30-day survival (ECPELLA: 53%, VA-ECMO: 20%, p < 0.01) and favorable neurological outcome determined by the Cerebral Performance Category score 1 or 2 (ECPELLA: 33%, VA-ECMO: 7%, p < 0.01) were significantly higher with ECPELLA. Patients receiving ECPELLA also showed significantly higher total mechanical circulatory support flow and lower arterial pulse pressure for the first 3 days (p < 0.01) of treatment. There were no statistical differences in safety profiles between treatment groups. Conclusion: ECPELLA may be associated with improved 30-day survival and neurological outcome in patients with refractory cardiac arrest.